In the trucking industry, pneumatic suspension systems are commonly used in attaching axles to a truck or a truck trailer. In a pneumatic suspension system, each axle is attached to the truck or truck trailer using suspension members and pressurized air bags. The air bags are generally attached between each axle and the frame or body of the truck or a frame or bed of the truck trailer.
A drawback of current pneumatic suspension systems is an inability to separately control a supply of air delivered to each axle individually. Operation of a representative pneumatic suspension system 100 according to the prior art is schematically illustrated in FIG. 8. In this example, the prior art system 100 is shown to include three axles 104, 106, and 108. Attached to each axle is a pair of suspension air bags arranged at opposite ends of the axle. Axle 104 includes air bags 112 and 132; axle 106 includes air bags 116 and 128; and axle 108 includes air bags 120 and 124. A pressurized air supply 110 delivers a flow of compressed air to each of the air bags. The air bags are shown fluidly connected in series. An air line 114 fluidly connects air supply 110 to air bag 112 associated with axles 106. Air bag 112 in turns is fluidly connected to air bag 116, associated with axle 106, via air line 118. Air line 122 fluidly connects air bag 116 to air bag 120, which in turn is fluidly connected to air bag 124 via air line 126. Air bags 120 and 124 are associated with axle 108. Air bag 124 is fluidly connected to air bag 128, associated with axle 106, via air line 130. Lastly, an air line 134 fluidly connects air bag 128 to air bag 132, associated with axle 104. Compressed air from air supply 110 passes sequentially through air bags 112, 116, 120, 124, 128, and 132. This particular arrangement, however, does not easily allow the air bags to be individually controlled. Thus, it would be desirable to provide a pneumatic suspension system with the ability to individually control the air supply to each set of air bags associated with a particular axle.